What is VPN Passthrough and How does it Work?

In today’s digital age, where remote work and online communication are the norm, the need for secure internet connections has never been greater. Virtual Private Networks (VPNs) are a popular way to enhance online security and privacy. However, when using a VPN, some devices may not work properly due to the VPN blocking certain protocols. This is where VPN passthrough comes in. In this article, we will explore what VPN passthrough is, how it works, and how it can benefit you. Whether you’re a seasoned VPN user or new to the world of online security, understanding VPN passthrough can help you make the most of your VPN connection and stay protected online.

Why do some routers need a VPN Passthrough?

There are generally two types of routers, those that can natively accept VPN connections, and those that can’t. The former can handle protocols like IPsec, PPTP, and L2TP and can be configured as a VPN server or a site-to-site VPN with another gateway.

However, the latter type of routers cannot support VPN traffic since they do not have the built-in technology to do so. To overcome this limitation, VPN passthrough is used, which allows VPN traffic to bypass the router’s block and reach the VPN gateway over the internet.

This feature is commonly found on home routers, and it supports both PPTP and IPsec VPNs, allowing outbound VPNs to be established by computers on a private network without affecting inbound VPN connections. This feature is called VPN passthrough since it enables VPN traffic to pass through the router without needing to open any ports or configure the router. It’s a fully automatic process that enhances the router’s capabilities and offers a reliable and secure VPN connection.

What is the Difference Between a VPN and a VPN Passthrough?

A VPN and VPN passthrough are two distinct concepts. A VPN, or virtual private network, is a secure connection that allows you to send and receive data over the internet as if you were directly connected to a private network. A VPN encrypts all internet traffic, providing a secure and private connection that protects your online activities from prying eyes.

On the other hand, VPN passthrough is a feature found on some routers that allows VPN traffic to pass through the router and reach the VPN server. This feature is necessary because some routers may block VPN traffic by default, preventing devices behind the router from establishing a VPN connection.

To summarize, a VPN is a secure and private connection that encrypts all internet traffic, while VPN passthrough is a router feature that allows VPN traffic to pass through the router and reach the VPN server. A VPN is used to secure your online activities and protect your privacy, while VPN passthrough is used to overcome router limitations that may prevent VPN traffic from passing through the router.

Why do you need a VPN Passthrough?

You may need VPN passthrough if your router does not natively support VPN connections. Some routers may block VPN traffic by default, preventing devices behind the router from establishing a VPN connection. In this case, VPN passthrough is necessary to allow VPN traffic to pass through the router and reach the VPN server.

VPN passthrough is also useful if you have multiple devices on your network that need to use a VPN connection simultaneously. For example, if you have a household with several people who want to use a VPN to access geo-restricted content or protect their online activities, you’ll need a router that supports VPN passthrough to ensure that all devices can use the VPN connection.

Furthermore, if you’re a business owner, you may need VPN passthrough to establish secure connections between multiple sites. VPN passthrough allows you to establish site-to-site VPN connections between different locations without needing to replace your existing router infrastructure.

In summary, you need VPN passthrough if your router does not natively support VPN connections or if you have multiple devices that need to use a VPN connection simultaneously. Additionally, VPN passthrough is useful for businesses that need to establish secure connections between different sites.

PPTP Passthrough

PPTP (Point-to-Point Tunneling Protocol) passthrough is a feature that allows PPTP traffic to pass through a router that does not natively support PPTP VPN connections. PPTP is an older VPN protocol that is less secure than more modern protocols like OpenVPN or IPSec, but it is still used by some older devices and systems.

When you initiate a PPTP VPN connection, your device sends VPN traffic through port 1723 to the VPN server. However, some routers may block this traffic by default, preventing your device from establishing a PPTP VPN connection. This is where PPTP passthrough comes in.

PPTP passthrough allows PPTP VPN traffic to pass through the router and reach the VPN server. When PPTP passthrough is enabled, the router will inspect the PPTP traffic and modify the IP headers so that the PPTP packets can be routed to the VPN server. Once the VPN server receives the packets, it will decrypt them and establish the PPTP VPN connection.

To enable PPTP passthrough, you’ll need to access your router’s configuration settings and locate the PPTP passthrough option. The exact location and name of this option may vary depending on your router model, but it’s typically found under the VPN or Firewall settings. Once you’ve located the PPTP passthrough option, simply enable it and save your changes.

IPSEC Passthrough

IPsec passthrough employs a NAT-T, or network address translator traversal, which facilitates the establishment and secure maintenance of IP connections over gateways that use NAT. To ensure proper functionality of IPsec VPNs with NAT protocol, NAT-T must be used; otherwise, traffic won’t be encrypted and no VPN tunneling will occur.

NAT-T packages the security payload within a UDP packet, which is recognized by NAT. The process is made more efficient due to the protocols that comprise IPsec, which need to be fully enabled to traverse firewalls and network address translators, including Internet Key Exchange (IKE) through UDP port 500, IPsec NAT traversal through UDP port 4500 when NAT traversal is operational, Encapsulating Security Payload (ESP) through IP protocol number 50, and Authentication Header (AH) through IP protocol number 51.

Numerous routers include specific features, known as IPsec passthrough, within their program. Additionally, all versions of Microsoft Windows that are supported have NAT traversal enabled by default, eliminating the need for any modifications to settings.

Should I disable my VPN passthrough?

Whether or not you should disable VPN Passthrough on your router or firewall depends on your specific needs and network setup.

VPN Passthrough is a feature that allows VPN traffic to pass through your router or firewall without being blocked, while still maintaining the encryption and security of the VPN connection. Disabling VPN Passthrough could potentially interfere with your ability to establish VPN connections from within your network, as the VPN traffic could be blocked by the router or firewall.

However, there are some cases where disabling VPN Passthrough may be necessary. For example, if you have security concerns and want to prevent any VPN traffic from passing through your network, or if you are experiencing issues with your network and suspect that VPN Passthrough may be causing problems.


Why should I allow VPN passthrough?

If you are using old VPN protocols like PPTP and L2TP, you should enable VPN passthrough. These protocols are not compatible with NAT, which routers use to route packets on network devices. However, modern VPN protocols work with NAT, so VPN passthrough is not necessary for them.

How can I enable VPN passthrough?

To check if VPN passthrough is enabled, access your router’s web-based setup page. Look for the VPN passthrough setting under the security or VPN tab. Turn on IPSec Passthrough, PPTP Passthrough, and L2TP Passthrough. If these options are allowed, you should be able to establish a VPN connection.

Is VPN passthrough safe?

No, the protocols used for VPN passthrough are not secure. They provide fast speeds but at the expense of security. If online security is a concern, disable VPN passthrough and use VPN connections with modern security protocols like OpenVPN.

Do all routers have VPN passthrough?

Most popular routers have built-in VPN passthrough to accommodate legacy users who use VPN connections that rely on IPSec, PPTP, and L2TP protocols. If you don’t use these protocols, enabling VPN passthrough is unnecessary.

Should I turn off NAT?

No, NAT is essential because it allows routers to redirect internet traffic to your devices. If you turn off NAT, you will lose internet connection as your router-connected devices use private IP addresses, and the router connects to the internet with a single registered external IP address.


If you need to use an older VPN protocol that your router doesn’t support, it’s necessary to enable VPN passthrough. However, this feature is now mostly of historical interest since newer routers generally support modern VPN protocols.

Several routers support VPN passthrough, with the Netgear WGR614 Wireless Router being the most reliable and efficient. It can support up to three simultaneous VPN connections. The Netgear FWAG114 ProSafe is also an option for end-to-end VPNs, also known as site-to-site VPNs, but is more expensive.

Overall, VPN passthrough has many benefits and few drawbacks. It allows for VPN usage with nearly all routers by overriding the default system settings.

In summary, enabling IPSec or PPTP VPN passthrough, depending on the router, can be a solution when a router cannot connect to a VPN, providing privacy and security.

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shahek raza
shahek raza
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